Crouching behind a stone balcony that overlooks Aleppo's Old City, Abu Ahmad lines up an armoured vehicle in the telescopic sight of his sniper rifle and squeezes the trigger.
Then the 25-year-old Syrian rebel breaks a cardinal rule in the sniper manual -- instead of playing phantom and slipping silently away, he remains rooted to his firing point.
He reloads his weapon, an old Russian-made Dragonov, brings the stock to his cheek and again surveys the military checkpoint at one of the entrances to the Old City, searching for another soldier foolish enough to show himself.
"We have firing points on roofs all around the district, but they don't know exactly where we are," says the young man from Marea, farther to the north in the rebel-held zone.
"They fire back sometimes, but nothing serious."
Abu Ahmad, a small and agile man, does not want his true identity to be revealed.
Before the rebellion, he fitted curtains for a living.
The sniper -- qannas in Arabic -- chose his new profession "because you have to be calm and concentrate," Abu Ahmad, in a sleeveless jacket and helmet, tells AFP.
He and two others spend their days on the balcony and inside the flat with its drawn shutters and curtains, and furniture intact.
"It belongs to a Kurdish family who left because it's too close to the front line," Abu Ahmad says.
To get to the actual firing point, he has to push open the door to the balcony and crawl over to a small hole for his rifle that has been hammered through the white stone wall.
Around 500 metres (yards) away are the high walls of the fortress-like citadel. Behind their arrow slits sit Syrian army snipers.
Abu Ahmad and his two comrades climb the stairs of the building at 5:00 am each day, entering through the back for cover.
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"We take turns on the balcony, relieving each other every three or four hours. The rest of the time we sleep and keep watch through binoculars," he says. "The aim is to not let them advance, to harass them relentlessly."
On the floor around him lie dozens of spent bullet casings, an open box of ammunition, a water bottle wrapped in a damp napkin, a walkie-talkie and some leftover food.
Abu Ahmad says he has killed "at least 20 of (President) Bashar al-Assad's soldiers," and wounded a hundred more. He aims at a helmet unwittingly protruding from some sandbags at an army position.
Click, comes the sound from his rifle. It has jammed.
Come nightfall the men withdraw from the building to sleep alongside the rest of their unit, stationed a few streets away.
Their commander, who goes by the name of Khattab, would ideally like his snipers to be in position 24 hours a day but does not have any night-vision binoculars.
"Arms dealers do not sell us any," he says, apparently oblivious to the open availability of some types on the Internet.
"It's the same for weapons," he says. "Bashar told all arms dealers in the region that he would pay more for whatever they might sell to us. They're very difficult to come by."
He takes two large wads of cash in 100-dollar bills from his pocket. "We have money. This rifle here," he says, pointing at a 7.62 calibre Belgian-made sniper rifle leaning against a couch, "we bought from a regime soldier for $4,000 (3,100 euros)."
One of Khattab's men pulls aside the window blind and peers through his binoculars.
"All the army checkpoints are under attack from posts like this one," the commander says. "They can only travel in armoured personnel carriers. Once we have better weapons, it will be the end for them."
The balcony, from which two or three rounds are fired a minute, could have long been blown away by one of the tanks further down on the roundabout.
But so far it has not.
"They don't dare come any closer," asserts Khattab. "We have booby-trapped the road with powerful explosives. They know this."